This invention is directed to an assembly including a dichromated gelatin hologram with layers on each side of the hologram which inhibit moisture penetration to the hologram layer to protect it to provide a long life.
Present-day holographic emulsions are dichromated gelatin film. Gelatin is highly hydrophilic, and when water is absorbed by the dichromated gelatin film, the moisture causes the film to swell. The swelling changes the wavelength of reflection type holograms and can lower the efficiency of both transmission and reflection holograms. Therefore, it is desirable to protect the holographic emulsion layers from moisture to maximize holographic life.